In a research or an experiment, electrical characteristics, reliability, stability and safety of the A.C. supplying device and the power parts in the state of reactance load or specific load are usually unable to be inspected and examined. Therefore much time, labor and resources are wasted. Although the passive components such as inducer and capacitor can be used to simulate loading characteristics, or direct connection with an actual load can also be used, the set up procedure is generally clumsy, not easy to handle, difficult to arrange, and difficult to increase or decrease the power level. Therefore, a practical active AC load simulator is required to overcome the above drawbacks. The present invention provides an active AC load simulator to simulate the waveforms of capacitive reactance, inductive reactance, impedance and any selective form of wave in an AC circuit for inspecting and examining if the AC supply, power part in the state of reactance load or specific load function normally. The AC supplying device mentioned above can be an AC supplier, frequency changer and non-stop current system stabilizer, etc. The present invention can also be applied to the test for power factor, AC meter, etc. Examples of the power part above are power semiconductor such as rectifier, SCR, TRIAC, any kind of transistor; relay such as capacity solid state relay; breaker, fuse; transformer, capacitor,